Electric contact making device



F. E. ROMMEL March 3, 1953 I I ELECTRIC CONTACT MAKING DEVICE 2SHEETSSHEET 1 Filed Nov 29, 1950 lnVen for;

fi M" 2, W

9 Attorneys March 3, 1953 F. E. ROMMEL 2,

ELECTRIC CONTACT MAKING DEVICE Filed NOV. 29, 1950 2 SHEETSSHEET 2Patented Mar. 3, 1953 UNITED STATES PATENT OFFICE England, assignor toTelephone Manufacturing Company; Limited, London, England, a. Britishcompany Application November 29, 1950, Serial N 0. 198,061. InGreatBritain December; 8, 1949 7 Claims.

This invention relates. to electric contact malt: ing devices of thetype such as i widely used in telecommunications apparatus and includinga p a ty of fixed, spacedali ncd an subst at tially parallel contactcarryingmcmbcrs, adaptedto cooperate with. a plurality of. alignedspaced contact carrying members movablein the direction of alignmenttoma-ke or breal; connections between the contacts carri d byhe resp vmembers.

Much attention has b.861 directed tothe design of the contact carryingmembers for electromagnetic relays of this type having multiple contactsets, contact set? being usedhere in the sense of that group ofcontactsbctween which connection is made or broken in the operatiQ l oithe relay. In relays at present in wide use, the con-. tacts are carriedat the ends of parallel flat spring members usually referredto assprings, the moving contacts being carried by springs'intermediate thefixed contacts. Inorder to secure reliability and uniformity ofperformance of relays of this type, particularly for telephoneapparatus, it is necessary for the spring pressures to be accuratelyadjusted and such adjustment is a slow, tedious and costly Operationinthe production of the relays.

The present invention has for its object to pro-.- vide an imp o ed formr r lay o he pe e.- ferred to and in which multiple contacts sets areused, and whore h ndi dual adius m nt o he contact carrying members canbe assisted by mechanical means.. in contrast to the. conventioarrangement where manual adjustment is largely necessary. The nventiolso hasior ts. ject to provide an improved method ofmanufacturingelectrical contact making devices of this kind.

The. present n nti n ns sts f on e tr c contact-making device of thetype referred to, comprising means for securing and spacing the fixedcontact carrying members independently of the moving contact carryingmembers, whereby the latter can be assembled without affecting thespacing of the fixed contacts and means for maintaining substantiallyconstant the spacing of themoving contacts.

The invention further includes an electric contact-making device of thetype referred to comprising means for supporting said fixed contactcarrying members in parallel spaced relationship, and means forsupporting said moving contacts independently of said first supportingmeans, and insulating means for maintaining substantially constant theseparation of said moving contacts.

At the present time it isthepractice to make elays ndol ctromasnc cal yop ra e swi es for telecommunication purposes with contact spr ngs h chare rr nee in a ta k or pil andare clamp d. ach t one c l wi h inte posinsulating spacers. The springs, are arranged usua ly w t a te na e. m vng and fixed n a springs, though the fixed springsare, of course,resilient. The fixed springs are arranged to rest each on a bulier, orstop, and the movingsprings rest on an insulating actuating membercoupled to the armature of the relay.

Thus, aconsiderable number of individual pairs or contacts have to beoperated simultaneously by. the armature of an elcctromagnet. As theelectric power and the space available for the com lete swit hi gd oe isin p act imite the mechanical pressure and thefarmature travel avai abloor operating t e co tacts nee s o b reduced to the lowest figurecompatible. with reliable operation. Experience shows that, witheconomical production methods, contact clearances in the order of .010"to .015," and a come plete armature travel in the order of .030 to .040are necessary to ensure reliable operation. These relatively smallvalues and the necessity of en r n r a eq e min mum ont tp u e have, inthe past, led to the development of the buff spring s whi h s now l s oersally ado ed for es sw chi de i s.

A bufi reds ring sotw ll husino u e a spring t e ufi r s ri g lam edbetwe n. s a ers in a s ring pile nd ton ionedasaih t he oi er. and amoving spring constituting the secondcon tact rri clamped between s aocsi e s m p n ile and ensionod aga ns a. bitin in pera ed by t earmature. The. ad ustment or the sp ngs. or uch, a p ing et, i cludehree rations w ich. ha e o e mad b h ndr- .i) Tensionhufi r spr n a aint bu er to value requ o s re co act r u ension mo ing spring asinstliitiug ic. an

(iii). B nd spring ips to; cbtaincorrcc o ta t clearance. Thesethreeadiustmcnt nced tobcmadewith- 1n narr w lim ts. n order o. nsur OIC leara e i the. non op ated PQS iQlI and min m m onta tpr ssu ein T3116operated p s ion with. a given armature travel, Contacts mounted,adjusted and operated in thisway have proved to be highly effioient andreliable. Their main disadvantage s h t of carrying out, by hand, theadjustments described aboveand at.- tempts to eliminate all or part ofmanual lustmg op r t n by pre=stressing the springs before assemblinghave not proved satisfactory. As a result, electromagnetic switchingdevices with a large number of contact pairs, such as cross barswitches, selective relay units and so on involve a high degree ofmanual adjustment, which has a considerable influence on theirmanufacturing cost.

In order to reduce this cost, a simplified type of contact system hasbeen suggested in the past for cross-bar switches. In this arrangement amoving spring forming one contact carrier, is clamped between insulatingspacers and tensioned against a driving pin. The second contact ismounted on a rigid bar which forms the second contact carrier and isfixed rigidly relative to the clamping spacers. Whereas in theconventional spring set described, the contact pressure is ensured bylifting the buffer spring off its buffer, in this case the contactpressure would be obtained by flexing the moving spring against therigid bar. The necessary contact adjustments are reduced to:

(i) Tension moving spring against lifting pin, (ii) Bend moving springtip to obtain correct contact clearance.

' These adjustments also need to be within narrow limits, and as theadjustments are not independent they are not so easily made as with thebuffer spring described.

-' The present invention is concerned with overcoming much of the timeand expense of adjusting relay contact carriers, and various ways ofcarrying the invention into effect will be described with reference tothe accompanying drawings in which:

i Figure 1 is a side elevation of a selective relay unit, partly insection,

Figure 2 is a front elevation of the same unit,

Figure 3 is a plan view of the contact arrangement of the unit, andFigures 4 and 5 are diagrams indicating modified forms of contacts.

This embodiment of the invention is a selective relay unit, of the typehaving a series of electromagnets, each with associated sets ofcontacts, and a main operating magnet; when one of the'series ofelectromagnets is operated no "contacts of the various sets areactuated, but operation of the main electromagnet causes to be operatedonly those contacts associated with the energised electromagnet. It isconvenient to fjrefer to the electromagnets of the series as the fingermagnets.

This relay unit comprises an open box frame IID within which are locatedfinger magnets II, in this case five in number. The finger magnets "aresecured to a magnetic support plate I2, fastened in the frame by screwsI3, connecting 'tags [4 for the magnets pass through the plate. Themagnets have armatures l which carry spring fingers I6 having at theirfree ends lugs .I6a and IBb formed thereon and bent respec- "tively'downwardly'and upwardly. The operation of a finger magnet causes thearmature to be drawn'rearwardly in to the position of the rearmostfinger shown in Figure 1. Thus no contacts are operated by thismovement, but lugs Iiia are brought into the position in which theyserve to couple movement from a main magnet to the contacts to beactuated.

The main magnet closely resembles a type adapted as standard in relaysused by the British 'Post Office and comprises a magnetic frame I1,

coil I8 and armature I9. The armature is ad- 'justably spring loaded bya helical spring 20;

.4 the fittings of the magnet are so well known as not to warrantfurther description, except that the pivoted armature carries a supportmember 2| for an operating bar 22 which lies below and adjacent the lugson the fingers I6.

The main contact assembly of the relay unit is disposed above, and issecured to the box frame Ill. This assembly includes a base plate 23secured to the frame by screws 24; the base plate, and the parts,including the contact-carrying members, which form part of the contactassembly can be detached as a sub-unit from the box frame.

The contact assembly includes contact-carrying springs arranged in fivevertical banks, disposed one above each finger magnet armature, andassociated with that armature. Each bank includes fixed contact carryingsprings 25 alternating with moving contact carrying springs 26. Thefixed springs are clamped between spacers 2'! formed of strips ofinsulating material, the spacers being secured by bolts 28. The freelength of the fixed springs, extending from the stack of spacers isshort, being less than one inch, and preferably of the order of half aninch.

The moving contact carrying springs are likewise mounted at one end inthe stack of spacers 21, but are not clamped therein, and are held in amanner to be described hereinafter, The moving springs 26 are shown asbeing of approximately the same length as the fixed springs but may beslightly longer.

The contacts on the springs are formed by suitably shaping the ends, andby coating these parts with an appropriate metal.

The contact ends of the moving springs of each bank are spaced from eachother by engaging and being located in one of five insulating members2%. These are formed each of a thin strip of sheet insulating materialwhich is stamped with a series of thin transverse slots 29a along itsone edge into which fit the ends of the moving springs of one bank. Theinsulating strip is guided for movement vertically by means of twoslotted guide plates 30 and 3| secured one to the top of the stack ofinsulating spacers 21 and the other to base plate 23, Conveniently, the-slots in the two plates are open ended, as shown in Figure 3 tofacilitate assembly. The downward movement of each strip in the slottedplates is limited by a shoulder 292) formed on the strip and adapted toengage the lower plate 3|. The bottom ends of each of the strips 29 areadapted to rest between the lugs I62) on the appropriate necessary toset up the moving springs either as to pressure or as to separation forthe reason that each spring, very near the contact, is located by theslots 29a in the strip 29. It is, of course, a relatively simple matterto manufacture the strips with a very high uniformity from one to thenext, and by this means a corresponding high degree of uniformity ofspacing of the moving contacts can be obtained. It is necessary for thesprings to fit with a working clearance in the slots, but this caneasily be made smaller than the tolerance in the desired spacing betweenfixed and moving springs.

With the arrangement described the movingsprings can be made as thin andlight as desired, since the springs are relieved of the duty of locatingthe contacts as in the usual arrangement and serve only to carry thecontacts and the electric current to them.

It is advantageous to provide double contacts on the carriers and theconstruction described lends itself particularly well to this. Thus themoving contact carriers can be made as shown in Figure 3, each with acentral stem portion 2611 which is relatively thin and narrow, anenlarged end portion 260 by which the spring is positioned in the stackof insulating spacers and an enlarged contact carrying end 262). Thelatter end is then forked, by slotting the enlarged portion and theinsulating strip 29 can then be located within the fork, with one arm ofthe fork on each side. Each arm is transversely corrugated at its endsto provide contact making portions.

The fixed contact springs are similarly made double to pass each side ofthe insulating strip and to engage the double moving contacts, but inthis case each spring is slotted back to the clamping point so as toprovide two virtually independent arms. Such independent arms can moreeasily accommodate themselves to small variations of dimensions or themoving contacts than can the comparatively short arms on the ends of aconventional twinned spring.

In spring sets of this type for cross bar switches in a selective relayunit for a cross bar system rows of springs may be connected together,it is then possible, with the construction described to make the fixedcontact springs as a single member. This member is stamped from a metalsheet and is shaped so that extending from the clamping line are pairsor independent springs as indicated at 25 in Figure 3. Sufiicient spaceis provided between each pair of springs to accommodate the width of theinsulating strip 29 operating the contacts so that the contacts properremain visible for inspection from the front of the spring set when thefinal assembly is completed.

The spring tips may be provided with contacts in the conventionalmanner, or, in order to further facilitate the automatic adjustment'andto reduce production cost, the complete row of springs may be blanked inone operation out of a strip of spring material with a suitablethickness of appropriate contact metal rolled on to the part which willform the spring tips, thus providing a surface of contact metal on thetips. The overall thickness of the springs is the same at the contactedsurfaces as on the rest of the length and this facilitates automaticadjusting.

The rigid contact springs may also be provided with contacts in theconventional way, or may embody locally rolled on contact metal as inthe case of the springs. In the latter case, in order to provide adefinite position of the contact, the contact carrier may be suitablycorrugated as shown or may have raised pips embossed into it. Thislatter operation may be performed in a manner suitable to increase theeffective thickness of the contact metal locally at the position of thecontact.

The springs may, of course, be embossed in a similar manner to providecounter contacts if desired.

Despite the fact that with the construction describedit is necessary toadjust only the fixed! contact springs, the adjustment of suchsprings inthe completed unit would nevertheless be dim-- cult owing toinaccessibility. It is an important.

feature of the present invention that the-fixed contact springs can beassembled and clamped before the moving springs are inserted in positionbetween them. This'is of great practical importance, since it is not adiificult matter to design an apparatus for straightening or adjustingonly the fixed springs when there is no obstruction by the movingsprings and this is particularly so with the present construction sinceaccurate spacing only of the springs is required.

The method by which the moving springs are carried is indicated inFigure 3. At the rear end of each moving spring is formed an enlargement26c and this serves as a stop to limit the'movement of the spring in aslot formed in the spacers 21 to receive it.

Theforward end of each moving spring isof course retained by theinsulating strip 29 so that the spring is therefore securely held in'thecompleted unit. In assembling the unit, therefore, the fixed springs areassembled clamped and adjusted; this adjustment is effected by bending,the springs in alternate directions, to a decreasing extent each time.The moving springs arethen dropped into the slots in the spacersprovided to receive them, withoutany release of the now adjusted, fixedsprings. The insulating strips are inserted, and held in position by theslotted plates 30 and 3|.

A separate restoring spring operating against the insulating strips maybe provided, but in the case where numerous springsare used the sum ofthe pressures exerted by the individual contact springs may besuflicient to provide the necessary restoring force. This measure stilldoes not constitute a reversion to the old lever spring principle as noindividual adjustment of springs is involved and one or more of themoving springs may even rest on the upper edge of the slot in theinsulating strip without detriment to the proper operation of the springset.

In a spring set with make contacts-built up in this manner, theoperating pressureto be provided by the armature is equal to the sumof-all contact pressures plus'the restoring pressure; It is, of course,desirable to keep the latter as low as'possible and, it is for thisreason, that-the cross sectionof the flexing length of the connectorstrips is kept as low as possible with due regard to mechanicalstability, and the length of this portion of the connectoras greatas-possible. At the same time, since there is no need to clamp themoving springs it is not difiicult to achieve a low restoring force,even with multiple springs. It will be seen also thatwith the slottedmounted arrangement for the moving spring the flexing length isincreased.

The fixed springs are kept short, as is pointed out above. This has theobvious merit of compactness, but in addition this reduces variations inthe position of the contact tips owing to small movements in theclamping edges of spacers, which may be caused by pressure changesresulting from alteration of temperature or humidity. As the springs cannow be automatically adjusted in toto by means of a tool, considerationsof accessibility no longer apply and the length of the spring can bereduced to a value determined only by production and contact pressureconsiderations, and the figure of half an inch becomes practicable. Thiscomparative shortness of the spring relative to the contact travel alsoincreases the rubbing which occurs and thus the self-cleaning propertiesof the contacts are improved.

In a modified form of contact spring shown in Figure 4 the fixed springsare located in a stack of insulating spacers, as described above, butthe moving springs each take the form of a wire 32. The end of the wireis bent at right angles and is passed through the insulating strip 29which is guided for vertical movement as before. The other ends of thewires pass freely through openings in the stack of insulating spacersand project behind the stack to provide connecting lugs at 32a. Withthis construction also it will be seen that the adjustment of the fixedsprings only is required, the spacing of the moving springs beingdetermined permanently by the ends of the wires secured in theinsulating strip.

In a modification of the arrangement described, the moving spring can bedispensed with as such, the moving contacts being rigidly supported uponan insulating member. Such an arrangement is shown diagrammatically inFigure 5; here'the fixed contact springs 25 are clamped in the pile ofspacers 21, but moving contacts 33 of a relatively short and rigidconstruction are secured to the insulating strip 29. The strip 29 isactuated as described above. Connection is made to the contacts 33 byany light conductors, such as thin foil connections 34. The foilconnections may be supported in the stack of spacers 21, or in aseparate stack, and with a relay unit for a cross bar system, instead ofconnecting the fixed contacts together, the moving contacts of thevarious banks can be joined by light foil connections.

I claim:

1. An electric contact making device comprising the combination with aplurality of fixed contact carrying members and a cooperating pluralityof movable contact carrying members; of insulating spacer means notchedto provide a plurality of slots for receiving the respective fixedcontact carrying members to support and space the same independently 0fthe movable contact carrying members, whereby the latter can beassembled without affecting the spacing of the fixed contacts, meanscomprising a bar of insulating material supporting the contactcarryingends of said movable contact carrying members and maintaining thespacing of the contacts thereon substantially constant, and meansincluding said bar for retaining said movable contact carrying memberswith portions thereof seated in said slots and in interleaved relationto the fixed contact carrying members.

2. An electric contact making device comprising a series ofsubstantially parallel fixed spring members, contacts on said fixedmembers, spacers of insulating material between said fixed membersadjacent the ends thereof, clamping means for clamping said fixedmembers and said spacers to hold said fixed members in spacedsubstantially parallel relationship, a series of movable contactcarrying members, contacts on said movable members, insulating spacingmeans for maintaining substantially constant the separation of thecontacts on said movable members, and means including said spacers andsaid insulating spacing means for removably supporting said movablecontact carrying members in cooperative relation to said fixed members,said spacers when assembled with said fixed members providing slots forthe entrance or removal of said movable members.

3. A device according to claim 2 wherein said insulating spacing meansare recessed to receive the ends of moving contact carrying members.

4. A device according to claim 2, wherein said movable contact carryingmembers comprise wires, and said insulating spacing means comprises abar of insulating material having openings therethrough through whichthe ends of the said wires pass.

5. A device according to claim 2, and comprising, as a part of saidmeans removably supporting said movable contact carrying members, meansguiding said insulating spacing means for linear movement; said movablecontact carrying members being seated in recesses in said insulatingspacer means, said movable members being thereby held against removalfrom said recesses and from said slots of said assembled spacers.

6. A device according to claim 2 wherein the said fixed contact carryingmembers are supported near one end thereof and the free contact carryingpart thereof is not greater than one inch in length.

'7. A device according to claim 6 wherein said part is of the order ofone half of an inch in length.

FREDERICK E. ROMMEL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,086,136 Reynolds July 6, 19372,348,088 Nichols May 2, 1944 2,385,858 Horman Oct. 2, 1945 2,390,344Ayers et al. Dec. 4, 1945 2,444,026 Bartelheim et al. June 29, 19482,500,413 Horlacher Mar. 14, 1950 2,523,360 Ellwood Sept. 26, 1950

